Apple this morning published its annual Supplier Responsibility Report to its website. The report details the company’s Supplier Code of Conduct and the lengths it has gone through in the past year to ensure its suppliers and their materials are on the up-and-up.

One of the more notable items from the report is that Apple says that all active, identified tantalum smelters in its supply chain were validated as conflict-free by third-party auditors. This means that all of Apple’s suppliers are using only verified tantalum sources…

The ethical sourcing of minerals is an important part of our mission to ensure safe and fair working conditions. In January 2014 we confirmed that all active, identified tantalum smelters in our supply chain were verified as conflict-free by third party auditors, and we’re pushing our suppliers of tin, tungsten, and gold just as hard to use verified sources. To heighten smelter accountability and help stakeholders follow our progress, we are releasing, for the first time, a list of the smelters andrefiners in our supply chain along with their verification status.

The procurement of tantalum—along with gold, tin and tungsten—has become a hot-button issue in the consumer electronics industry because minerals from some of the mines in the Democratic Republic of the Congo are believed to be funding fighting in the area.

In fact, the issue is important enough that Apple’s senior vice president of operations Jeff Williams spoke to The Wall Street Journal on the topic. He tells the news outlet that Apple is working with various third-party auditors to identify good and bad tantalum mines.

“In the company’s 2014 Supplier Responsibility report published on Wednesday, Apple identified that its suppliers use 20 global smelters or refiners whose tantalum has been verified by third-party auditors as what the industry calls “conflict-free.” Jeff Williams, Apple’s senior vice president of operations, said the company has had success in pressuring tantalum smelters to agree to a third-party audit because Apple and other consumer electronics firms are the biggest users of the metal.”

Apple’s report also noted that it is tracking the weekly hours for over 1 million of its supply chain workers, and that 95% of its suppliers are in compliance of its standard maximum 60-hour workweek. Weekly hours is often a bone of contention for labor rights groups.